EP3857685A1

EP3857685A1 - Electric actuator

Info

Publication number: EP3857685A1
Application number: EP19773870.1A
Authority: EP
Inventors: Cédric MELLERE
Original assignee: Sonceboz Mechatronics Boncourt SA
Current assignee: Sonceboz Mechatronics Boncourt SA
Priority date: 2018-09-28
Filing date: 2019-09-30
Publication date: 2021-08-04
Also published as: FR3086814A1; CN112771770A; WO2020065088A1; US20210351682A1; FR3086814B1

Abstract

The invention relates to an electric actuator comprising a housing (2), an electric motor comprising a wound stator and a rotor mounted on a shaft, a printed circuit for powering the stator, an intermediate plate (3), a mechanical reduction gear driven by said rotor and comprising toothed wheels mounted on axes, a cover (4) and two centring pins (8a, 8b). The motor is housed in a cavity of the housing (2) which guides one end of the shaft. The printed circuit is located above the stator. The intermediate plate (3) is located above the printed circuit. The cover (4) is located above the intermediate plate (3). The reduction gear is housed in a cavity of the cover (4) which guides one end of each axis. The intermediate plate (3) guides the other end of the shaft and of the axes. Three pairs of centring holes (7, 9, 12) receive the centring pins (8). The housing (2) comprises a single sealing gasket (6) positioned at the interface between the housing (2) and the cover (4)

Description

ELECTRIC ACTUATOR

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field of electric actuators comprising the assembly, in a housing and a cover, of an electric motor, a printed circuit carrying the electronic control components and a mechanical reducer.

STATE OF THE PRIOR ART

It is already known in the state of the art of many electric actuators. For example, documents WO2018 / 088356 which describes an actuator which is provided with: a housing which has a motor housing and a gear housing each having an opening on one side and in which the motor housing and the housing d 'gears are assembled to each other so that the respective openings face each other; a motor which is installed in the motor housing; a gear which is installed in the gear housing and which is arranged so as to transmit the rotation of the motor. The housing has a partition wall which is arranged between the motor and the gear. The gear is rotatably supported on both sides in the direction of the gear shaft by the gear housing and the partition wall. According to this solution, the housing comprises a first and a second motor housing open on one side, and a central housing disposed between these two housings. It is The housing sandwiches the central housing between the motor housing and the gear housing.

This solution involves providing a double seal, on the one hand between the central housing and the first motor housing, and on the other hand between the gear housing and the central housing.

We also know the patent applications US2018 / 062479, DE4313782 and WO2010 / 138455 describe actuator constructions comprising a printed circuit positioned between an electric motor and a mechanical reducer. These achievements, although compact and capable of producing high torques, lack robustness to provide performance in vibration resistance and sufficient service life. Indeed, endurance performance requires alignment, precise and controlled centering of the guide elements of the mechanical gearbox as well as efficient management of the evacuation of the thermal energy produced at the level of the electronic components and of the engine. The embodiments claimed in these documents provide no solution for the robust control of the precise guiding of the reducer (imperfect guiding because only present on one side of the wheels forming this reducer, favoring harmful overhangs, lack of precise centering between the housing and the cover forming the upper and lower guide elements of the reducer, promoting faults in coaxiality and parallelism). These achievements also do not provide any solution for the dissipation of thermal energy, the electronic components present on the printed circuit having no thermal bridge to the outside to dissipate the thermal energy which they produce, favoring harmful overheating. . This results in solutions that are not mechanically robust and incapable of addressing applications at high operating ambient temperature and / or at high operating load.

There are solutions that overcome the drawbacks mentioned above, as for example described in the document WO2010138455, thanks to the use of an intermediate plate located between the electric motor with its printed circuit on the one hand and the reducer. mechanical on the other hand.

This solution allows to resume the guiding of the shafts of the mechanical reducer and also allows improved heat dissipation at the level of the printed circuit by its proximity to the latter. This solution also offers a liquid cooling circuit which circulates in the peripheral proximity of the engine for better evacuation of thermal energy.

However, the implementation of this intermediate plate is not easy: on the one hand it has a rigid support on the cover but it is supported on the housing side on the very slightly rigid printed circuit, and on the other apart it does not integrate any centering element allowing adequate guidance of the three elements: housing, cover and intermediate plate. In addition, the document cited above does not give a solution to the consequent hyperstatic mechanical situation of this bilateral support and of the need to close the actuator in a sealed manner. STATEMENT OF THE INVENTION

The present invention relates to an improvement of current solutions, in particular by proposing an effective industrial solution allowing the centering and the viable guidance of the three elements mentioned above.

The present invention also aims to provide a solution to the hyperstatic mounting described above, promoting the robustness of the mounting of the actuator.

The present invention also aims to improve the thermal behavior of the actuator, allowing its use in environments brought to high temperatures (typically above 150 ° C).

More particularly the invention relates to an electric actuator comprising a housing, an electric motor comprising a wound stator and a rotor mounted on a rotor shaft, a printed circuit for supplying said stator and driving said motor, a intermediate plate, a mechanical reducer driven by said rotor and formed of toothed wheels mounted on axes, a cover, two centering pins, said housing defining a first cavity in which is housed said stator, said housing serving to guide said rotor shaft on a first end, said printed circuit being housed in said first cavity above said stator, said intermediate plate being located above said printed circuit, said cover defining a second cavity provided with guide means one of the ends of said axes of said mechanical reducer and being located above said intermediate plate, said p intermediate lacquer having means for guiding the other end of said rotor shaft, and serving for guiding the other ends of said axes of said mechanical reducer, characterized in that in the first cavity of said housing has a first pair of centering holes receiving said two centering pins, in said intermediate plate has a second pair of centering holes receiving said two centering pins, in said cover has a third pair of centering holes receiving said two centering pins, said intermediate plate is in contact with said housing and said cover on surfaces of support located around the centering holes, two of said first, second and third pairs of holes are composed of a cylindrical centering device and a cleared centering device, the corresponding cylindrical centering devices and clearing centering devices, the other of said first, second and third pairs of holes is composed of two cylindrical centralizers, said housing comprising a single seal positioned at the interface between the housing and the cover.

“Cylindrical centering device” is understood to mean a positioning pin which achieves a sliding pivot connection with two degrees of freedom (translation and rotation along an axis only)

By “cleared center” is meant a positioning pin which achieves a straight linear connection, with four degrees of freedom, or a point connection, with 5 degrees of freedom.

Thus, an actuator according to the invention can solve the above problems, regardless of the element (cover, case or intermediate plate) which has the two cylindrical centralizers.

Preferably, said casing comprises a perimeter of a casing having at least two first fixing bores and in that said cover comprises a perimeter of a covering having at least two second fixing bores so that the fixing of said cover and said case is made by screwing using said first and second holes, said case and cover edges not being contiguous when said cover and said case are supported on said intermediate plate before screwing and being in support and at least partially contiguous after screwing, so as to constrain and block the movement of said intermediate plate. The hyperstatism problem described above above is thus turned to the advantage of the actuator and the maintenance of the intermediate plate.

In an alternative embodiment, the cover forms a valve body.

Preferably, the different guide surfaces of said shafts and axes of the reduction gear train are produced by the housing, the intermediate plate and the cover, said guide surfaces being ball bearings or plain bearings.

In an alternative embodiment, said two centering pins and said intermediate plate form a single piece, in order to facilitate the overall production and assembly.

In another alternative embodiment, the housing is produced by overmolding a plastic material and has on one of the holes in the pair of centering holes two coaxial centralizers, one cylindrical, the other clear. This configuration makes it possible to envisage a single box, whatever the embodiment chosen for mounting and assembling the actuator, by playing on the length of the centering pin engaging this centering hole.

In another alternative embodiment, the housing is produced by overmolding of a plastic material and it comprises a connector integrated in the overmolding.

In order to hold higher operating temperatures, in a particular embodiment, the printed circuit has a first face receiving electronic components and a second free face of components, said first face facing the electric motor and at the bottom. of the housing, said second face facing the intermediate plate.

Then, advantageously and optionally, the first and second faces of the printed circuit are covered at least partially with a thermal paste also being at least partially in contact with, respectively, the housing and the intermediate plate. In order to improve the performance of the actuator, in another alternative embodiment, the wound stator has stator teeth tangentially extended by magnetic field collectors, at least part of said teeth carry coils and are attached to the stator and said coils have a frustoconical shape.

In this embodiment, in another alternative embodiment, each stator tooth carrying a coil has, with two adjacent teeth, a W shape, the outer flanks of the frustoconical coil being parallel to the inner flanks of said adjacent teeth. To optimize the performance of this embodiment, if D denotes the number of stator teeth and GAP denotes the tangential distance between the field collectors between two adjacent teeth, the relationship will be favored:

GAP is equal to 360 / (8xD) ± 5%.

Still in this same embodiment, to optimize performance, if E denotes the radial thickness of the rotor magnet, if EP1 denotes the minimum radial thickness at the end of the field collector and EP2 denotes l maximum radial thickness at the birth of the field collector, the relation:

EP2> 0.75xE and EP1 <EP2. Finally, in a desire to simplify the electric machine of the actuator and improve performance, the rotor comprises a permanent magnet partially overmolded by an injected plastic, this overmolding partially encompassing the rotor shaft and forming a plane orthogonal to the shaft on which a sensor magnet is positioned. In an alternative embodiment, the overmolded magnet directly forms a sensor magnet without adding an additional magnet.

BRIEF DESCRIPTION OF THE FIGURES Other characteristics and advantages of the invention will emerge on reading the following detailed exemplary embodiments, with reference to the appended figures which represent respectively:

- Figure 1, an exploded perspective view of a first actuator according to a first embodiment,

FIG. 2, an exploded perspective view of the first actuator according to a second embodiment,

FIG. 3, an exploded perspective view of the first actuator according to a third embodiment,

FIG. 4, an exploded perspective view of a second actuator according to a first embodiment,

FIG. 5, an exploded perspective view of the second actuator according to a second embodiment,

FIG. 6, an exploded perspective view of the second actuator according to a third embodiment,

FIG. 7, a first detailed view in section of the second actuator according to the second embodiment,

FIG. 8, a second detail view in section of the second actuator according to the second embodiment,

FIG. 9, a perspective view in section of the second actuator according to the second embodiment,

FIG. 10, an overall perspective view of the second actuator,

FIG. 11, a perspective view in partial section of the actuator of FIG. 10,

FIG. 12, an isolated overall view of a housing and an intermediate plate of the second actuator,

- Figure 13, a perspective view in partial section of the assembly of Figure 12,

FIG. 14, a view in partial section of the second actuator in an alternative embodiment, FIG. 15, an overall perspective view of the first actuator in an alternative embodiment,

FIG. 16, a perspective view in partial section of the actuator of FIG. 15,

FIG. 17, an isolated overall view of a housing and an intermediate plate of the first actuator in an alternative embodiment,

- Figure 18, a perspective view in partial section of the assembly of Figure 17,

FIGS. 19a and 19b, two views in partial section according to two different viewing angles of the first actuator in an alternative embodiment,

FIG. 20, an isolated sectional view of an electric motor of the second actuator,

FIG. 21, an isolated view of an electric motor stator integrated into the first or second actuator in an alternative embodiment,

FIG. 22, an isolated and partially exploded view of the stator of FIG. 21,

- Figure 23, an isolated view in cross section of the stator of Figure

21,

FIG. 24, an isolated view in longitudinal section of an electric motor rotor in an alternative embodiment,

- Figure 25, a partial sectional view of an actuator according to an alternative embodiment of the mechanical reducer,

FIG. 26, an isolated view of an alternative embodiment of an electric motor rotor which can be used in an actuator according to the present invention,

FIGS. 27 and 28, two views in partial section showing alternative embodiments of the stators of an electric motor which can be used in an actuator according to the present invention,

FIG. 29, an exploded perspective view of an actuator according to an alternative embodiment,

- Figure 30, a partial sectional view of the actuator of Figure 29. DETAILED DESCRIPTION OF A FIRST ACTUATOR

In Figure 1 is presented a first embodiment of an actuator (1) according to the invention. Generally and common to all the embodiments covered by the invention, the actuator (1) is formed by three main parts: a housing (2), an intermediate plate (3) and a cover (4). We also see in this figure 1, as well as certain other figures, fixing screws (5) and a seal (6) whose positioning will be explained later. This seal (6) is the only seal ensuring the seal between the housing and the cover, while in the solutions of the prior art and in particular patent WO2018 / 088356, it is necessary to provide two seals.

This Figure 1 shows a first example of an actuator in which the housing (2) is made of an injectable plastic. This housing (2) has in particular the function of accommodating an electric motor (not visible here) which will be detailed below, by overmolding the stator of this motor with said plastic material. The purpose of the cover (4) is to accommodate in particular a mechanical reducer (not visible here) which will be detailed below. The purpose of the intermediate plate (3) is to guide the rotating elements of the mechanical reduction gear while allowing the mechanical connection between the rotor of the electric motor and the mechanical reduction gear. The seal (6) is intended to be positioned at the interface between the housing (2) and the cover (4) so as to produce a seal by axial crushing during assembly. The fixing screws (5) are intended to fix the housing (2) on the cover (4) at the threads (1 1) by constraining the intermediate plate as will be explained below. The internal threads (1 1) can also be blind holes in which self-forming screws are screwed.

The support of the intermediate plate is located - only - around the centering holes receiving the pins (8a, 8b), which allows in particular to place a single seal at the interface between the cover and the housing and improve the tightness compared to the solution proposed in the document of the prior art WO2018 / 088356. In a first embodiment of the invention linked to this first actuator (1), the housing (2) plastic has, not visible here, a first pair of holes formed by a cylindrical centralizer and a cleared centralizer; the intermediate plate (3) has a second pair of holes in the form of two holes, or cylindrical centralizers (7a, 7b) which receive two centering pins (8a, 8b).

These two centering pins (8a, 8b) can be: o Either dissociated from the intermediate plate and introduced downstream of the manufacture of the plate o Either integrated into the intermediate plate and therefore form a single piece with the plate forming then a unique piece.

The cover (4) has a third pair of holes formed by a cylindrical centering device (9a) and a free centering device (9c) here in the form of an oblong hole. The clever use of only two pins and three pairs of holes on the three main elements mentioned above, of which two of the pairs of holes form cylindrical centralizers and cleared centralizers and of which the other pair of holes forms two cylindrical centralizers , the corresponding cylindrical and cleared centralizers, ensures an optimal relative positioning of said three elements. The positioning of the pins (8a, 8b) on the intermediate plate (3) in cylindrical centralizers (7a, 7b) represents the preferred configuration because it makes it possible to envisage a single type of intermediate plate (3) compatible with several forms of housing ( 2) and / or cover (4).

Figure 2 is a second embodiment of this first actuator which differs from the first mode in that the centering pins (8a, 8b) are positioned in the pair of holes in the cover (4), forming two cylindrical centralizers (9a, 9b) and in that the intermediate plate (3) comprises a pair of holes forming a cylindrical centering device (7a) and a free centering device (7c). As for the first embodiment, the plastic case (2) has, not visible here, a pair of holes formed by a cylindrical centering device and a cleared centering device. It is an alternative embodiment to the first mode. A third alternative embodiment of this first actuator is presented in Figure 3. It differs from the first and second modes in that the centering pins (8a, 8b) are positioned in the pair of holes in the plastic case (2) , forming two cylindrical centering devices (12a, 12b) and in that the intermediate plate (3) comprises a pair of holes forming a cylindrical centering device (7a) and a free centering device (7c). As for the first embodiment, the cover (4) has, not visible here, a pair of holes formed by a cylindrical centering device and a cleared centering device.

DETAILED DESCRIPTION OF A SECOND ACTUATOR

Figures 4, 5 and 6 show, for a second type of actuator, the equivalents to Figures 1, 2 and 3 in terms of the relative positioning of the different pairs of cylindrical and cleared holes and centralizers. The second actuator differs from the first in that the housing (2) is here formed from a metallic material, for example from molded or injected aluminum, in which is intended to be fixed, for example by screwing, the stator of an electric motor . This embodiment makes it possible to produce a more robust actuator making it possible in particular to better dissipate the thermal energy released by the printed circuit (not shown in these figures) carrying the power supply and control components of the motor and by the electric motor. The second actuator also differs from the first in that the fixing screws (5) are intended to be screwed into the housing (2) instead of the cover (4). Finally, it differs from the first in that the seal (6) performs a seal by radial compression of the seal (6). Similar to the explanations in Figures 1, 2 and 3:

In a first embodiment of the invention linked to this second actuator in FIG. 4, the metal casing (2) has, not visible here, a first pair of holes formed by a cylindrical centering device and a cleared centering device; the intermediate plate (3) has a second pair of holes in the form of two cylindrical centralizers (7a, 7b) which receive two centering pins (8a, 8b) and the cover (4) has a third pair of holes formed by a cylindrical centering device (9a) and a free centering device (9c) here in the form of an oblong hole. Figure 5 is a second embodiment of this second actuator which differs from the first mode in that the centering pins (8a, 8b) are positioned in the pair of holes in the cover (4), forming two cylindrical centralizers (9a, 9b) and in that the intermediate plate (3) comprises a pair of holes forming a cylindrical centering device (7a) and a free centering device (7c). As for the first embodiment, the metal case (2) has, not visible here, a pair of holes formed by a cylindrical centering device and a cleared centering device. It is an alternative embodiment to the first mode.

A third alternative embodiment of this second actuator is presented in Figure 6. It differs from the first and second modes in that the centering pins (8a, 8b) are positioned in the pair of holes in the metal case (2) , forming two cylindrical centering devices (12a, 12b) and in that the intermediate plate (3) comprises a pair of holes forming a cylindrical centering device (7a) and a free centering device (7c). As for the first embodiment, the cover (4) has, not visible here, a pair of holes formed by a cylindrical centering device and a cleared centering device.

DETAILED DESCRIPTION OF THE MAIN DUTIES

Figures 7, 8 and 9 are detail views or in section of the second embodiment of the second actuator. Nevertheless, the descriptions and characteristics of the elements and of the functions which relate thereto below can fully apply, mutatis mutandis, to the other embodiments described above.

FIGS. 7 and 8 are isolated views at the level of the centralizers, respectively free (7c, 12c) and cylindrical (7a, 12a) produced on the intermediate plate (3) and the case (2), allowing mounting, guiding and blocking the rotation of the latter on the centering pins (8a, 8b) placed respectively in the cylindrical centralizers (9a, 9b) of the cover (4). The intermediate plate (3) is held axially between the housing (2) and the cover (4) by the stress exerted by the latter at the level of two axial bearing surfaces (13, 14) around the centering holes between, respectively , on the one hand the case (2) and the plate intermediate (3) and on the other hand between the intermediate plate (3) and the cover (4). Referring to Figure 9, the intermediate plate (3) is installed in a first cavity (15) of the housing (2). Thus, when the cover (4) is screwed onto the housing (2) - or of the housing (2) on the cover (4) for an embodiment of the first actuator - the periphery (16) of the housing (2) comes in the vicinity of the periphery (17) of the cover (4), first without contact and then, by the elasticity of the components involved, with contact as the screwing takes place, and the hyperstatic mechanical situation generated at the constrained connection between the housing (2), intermediate plate (3) and cover (4) ensures perfect retention of the intermediate plate (3) via the elasticity of the periphery (17). The screw-mounted actuator (1) is thus visible in Figure 9.

Referring to Figure 8, the actuator is sealed by the seal (6) positioned around a first radial surface (131) of the cover (4) and inside a second radial surface (133) of the housing (2) and between a first axial surface (132) of the cover (4) and a second axial surface (134) of the housing (2), the terms "axial" and "radial" being interpreted relative to the motor output axis. In this embodiment of the actuator, the sealing is achieved radially by the crushing of the seal (6) between these first and second surfaces (131, 133).

Figures 10 and 1 1 show overall views, respectively whole and in partial section, of the second actuator in a first variant called "complete" where this actuator can be positioned at an external member (not shown) thanks to its output shaft (18). The actuator (1) is supplied with electrical voltage and a positioning signal by a connector (19). The housing (2) receives in its cavity (15) an electric motor formed by a stator (20) and a rotor (not visible) as well as a printed circuit (22) in electrical connection with the stator winding ( 20) by a press-fit type connector and in mechanical connection screwed into the cavity (15) of the housing (2). The housing (2) receives a ball bearing (23a) used for guiding the rotor shaft (not visible here). A mechanical reducer (24), positioned in the cover (4), is driven by said rotor and is formed by toothed wheels mounted on axes (not visible). The cover (4) defines a second cavity (25) in which are mounted and guided on a first end said axes of said mechanical reducer carrying a toothed wheel (45a) by means of bearings (23c-23d). The intermediate plate (3) is used for guiding one end of the shaft (29) of the rotor, not visible here but presented in FIG. 12, thanks to the bearing (23b), not visible here but presented in FIG. 12, and serves guiding the other ends of the axes of the mechanical reducer (24) by means of bearings (23c, 23e). In this embodiment, without this being limiting, a torsion spring (26) is also installed in the cover (4) applying a torque to the output shaft (18) making it possible to bring the mobile assembly back to a predefined position when the electric motor supply goes out or fails. It should also be noted that the various bearings (23a, 23b, 23c, 23d, 23e, 23g, 23h) designated in all of the figures can be replaced by plain bearings or any other guide element without this being aside from the invention.

DETAILED DESCRIPTION OF THE ALTERNATIVE EMBODIMENTS

Figures 12 and 13 show the second actuator in a second variant called "half-actuator" where a first set (27) of the actuator is shaped by assembling the housing (2) and the intermediate plate (3 ) according to the third embodiment described above. The complete actuator is then produced by assembling this first assembly (27) on the cover (4) as shown in FIG. 14. In this particular embodiment, the cover (4) directly integrates the member to be controlled. By way of example given in this FIG. 14, the cover (4) forms a valve body (28) and the output shaft (18) carries a flap (30) of the "butterfly" type, the whole forming a valve. air intake for an internal combustion engine. When mounting the actuator (1), the first assembly (27) is therefore mounted directly on the valve body (28) forming the cover (4) and the mechanical reducer (24) engages, through a light (31 ) of the intermediate plate (3), the shaft (29) of the rotor (21).

Figure 13 shows a partial sectional view of the first assembly (27) which allows to view the printed circuit (22) which includes all electronic components used to power and control the actuator motor (1), as well as the ball bearing (23b) used to guide the shaft (29) of the rotor (21) whose outer ring is adjusted in a housing of the intermediate plate (3). Figures 15 and 16 show the first actuator in a variant

"Complete" where the connector (19) is molded in plastic material with the body of the case (2). Its orientation is radial but it can also be considered axial above the housing (2). The opening (32) visible in the cover (4) is an inlet for a heat transfer fluid used for cooling the actuator (1) when the latter is used at high load and in an environment brought to high temperature, for example near an internal combustion engine.

Figure 16 is a partial sectional view to assess the relative positioning of the bearings (23a, 23d) and the stator (20) in the housing (2), separated by the intermediate plate (3) of the mechanical reducer (24) and the torsion spring (26). At the level of the housing (2), this variant also has two coaxial centralizers, one being cylindrical (12b), the other being free (12c). This combined embodiment makes it possible to envisage the use of a single type of overmolding compatible with the three different embodiments described in Figures 1, 2 and 3, in conjunction with the height of the centering pin (8b) used. Here in FIG. 16, the elements of the complete actuator are mounted according to the first embodiment, the centering pin (8b) is a short pin which engages in the released centralizer (12c) of the housing (2).

Figures 17 and 18 show a variant "half-actuator" of the first actuator formed by a first assembly (27) comprising the housing (2) and the intermediate plate (3). In this variant, the centering pin (8b) is a long pin which engages in the cylindrical centralizer (12b) of the housing (2), the assembly being according to the third embodiment described above.

FIGS. 19a and 19b show an alternative embodiment of the actuators, here on the basis of the first actuator although this is not limiting, at the level of the printed circuit (22) and promoting the heat dissipation emitted by the printed circuit (22). In this variant, the printed circuit (22) carries all of the components on only one of its faces, this first face (33) being that oriented axially towards the electric motor and the bottom of the housing (2). This embodiment makes it possible on the one hand to attach the second face (34) of the printed circuit, axially opposite to the first face (33), to the intermediate plate (3), which will favor by conduction - the intermediate plate being chosen by a thermally conductive material -, the evacuation of calories by the metal part of the cover (4). On the other hand, it is possible to use a thermal paste - in a point cloud on the printed circuit (22) - on both sides of the printed circuit (22), this paste being crushed between the housing (2) and the plate intermediate (3) on the one hand and the cover (4) and the intermediate plate (3) on the other hand, in order to further promote this thermal conduction to the most conductive parts of the actuator (1). In these figures 19a and 19b is visible the output gear wheel (45c) of the reducer, as well as a torsion spring (26) which acts on this output gear to bring the output shaft (18) into a position determined when the engine supply stopped.

In Figure 20, showing a detailed view of the electric motor in section, is shown the use of a magnet (35) to the rotor (21), the length of which can be variable in order to increase the performance of the engine. Indeed, at a given axial height of stator (20), the axial height of the magnet (35) to the rotor (21) influences the torque produced at constant electrical power. This embodiment is only a variant compared to a more conventional case where the height of the magnet (35) is equivalent to that of the stator (20).

Figures 21, 22 and 23 show an example of an electric motor stator (20) which can be used by the first or second actuator or any other actuator not shown here but covered by the present invention. In particular, this stator (20) proposes to solve the problems of limitation of the performance of the actuators, in particular the limitations induced by the torque oscillation during electrical switching and by the magnetostatic torque. This stator (20) is also associated with a solution for optimizing the copper filling of the coil.

For this stator (20), all of the stator teeth (36a, 36b) have field collectors (37) extending, relative to the axis of rotation of the rotor, in a tangential direction. For this purpose, the teeth (36a) not receiving a coil are in one piece with the rest of the stator iron circuit made in the form of a sheet pack while the teeth (36b) receiving a coil (38) are independent and brought back to the iron circuit. In order to optimize the performance of the actuator, in particular the torque oscillation and the magnetostatic torque, the field collectors have the following geometric characteristics in an axial plane: relatively to a quantity D representing the number of teeth on the stator, we recommends respecting the formula:

GAP "360 / (8xD), GAP representing the tangential distance separating the collectors from two adjacent teeth; Relative to the quantity E, radial thickness of the rotor magnet visible in FIG. 20, we recommend:

EP2> 0.75xE and EP1 <EP2, EP1 representing the minimum radial thickness at the end of the field collector (37), EP2 representing the maximum radial thickness at the start of the field collector (37). The teeth (36b) have a central section allowing the positioning of the coil (38) by translation from the outside / rear. Likewise, the connecting means (mechanical and magnetic) between the attached tooth (36b) and the stator circuit is inscribed in the minimum section of the coil (38). One can also consider a winding solution directly on the tooth while retaining the possibility of removing the coil (38) and recovering the tooth (36b) in the event of a manufacturing defect. The teeth (36b) thus equipped with their coil (38) are attached and linked to the stator (20) in an axial direction relative to the axis of rotation of the rotor (21). The connecting means must ensure good mechanical retention of the tooth (36b) on the stator (20) and it must also ensure a good quality magnetic seal so as not to introduce parasitic magnetic permeance deteriorating performance. A dovetail type solution is particularly indicated in this case, allowing an economical solution, simple shapes with precise tolerances and good mechanical support. The coil body (39) has recesses (40), here 3 in number without this being limiting, on either side of the coils (38) for the press-on bearings on the tooth (36b) during the assembly operation. The stator circuit having a W-shaped periodicity over an angular sector of 120 °, the coil (38) then has a shape complementary to this W in order to maximize the copper filling rate of the section actually available. The shape of the winding thus obtained is of substantially frustoconical shape. The proposed conical solution allows a gain on the torque without significantly altering the impedance of the coil by an optimized filling of the inter-dental notch.

To achieve and industrialize this particular type of winding, the coil body (39) has a peripheral central sawtooth section, the angle of the teeth (43) being equivalent to the angle of the cone of the winding (approximately 7 ° in this nonlimiting example), the number of teeth (43) being 2 or more, the teeth (43) not necessarily being of identical length. In order to ensure good cohesion of the stator (20) thus assembled, and to improve its thermal behavior, it will ideally, but not limited to, be overmolded with a thermoplastic material located at the level of each pair of teeth (36b) / coil ( 38) reported. Alternatively, each tooth (36b) can be molded independently before being attached and fixed to the stator.

Figure 24 shows an embodiment of the rotor (21) of an electric machine, which can be advantageously used in the present invention. This rotor (21) is composed of a permanent magnet (35) partially overmolded by an injected plastic, a shaft (29) also overmolded by the same plastic, and a sensor magnet (41) positioned on a plane (42) orthogonal to the shaft (29) generated by the plastic, the rotor here being shown with the bearings (23a, 23b) described above. This achievement is particularly advantageous because it avoids the bonding of the magnet (35) on a cylinder head with mechanical resistance to problematic high temperature. It also makes it possible to increase the dynamic behavior via a lower inductance on the one hand by the absence of ferromagnetic yoke and on the other hand by a lower inertia due to the low density of the plastic material here predominant in volume. In addition, in addition to a simplification of the mounting of the rotor (21) which no longer requires a bonding operation, the magnetostatic torque and the friction torque are reduced just like the radial forces induced on the rotor.

Figure 25 is a partial sectional view which allows to observe the mechanical reducer (24). This mechanical reducer can be made up of several stages. The embodiments presented in the previous figures show two reduction stages, while the example of this figure 25 shows three reduction stages. Indeed, the rotor shaft (29) forming a pinion at its end drives the intermediate wheel (45a) carried by an axis (46a) guided by two bearings (23g, 23h), which in turn drives the toothed wheel ( 45b) carried by the axis (46b). The toothed wheel (45b) finally drives the output wheel (45c). As in all the embodiments presented in this text, all the axes (46a, 46b) or shaft (18) carrying the toothed wheels (45a, 45b, 45c) are on the one hand carried on the cover (2) on one of their end and on the other hand carried on the intermediate plate (3) on the other of their end.

Figure 26 shows a rotor (21) in an alternative embodiment. In the previous embodiments, this rotor (21) has a magnet of cylindrical shape carried or not by a ferromagnetic yoke. In this present exemplary embodiment, the rotor (21) consists of alternating magnets (35a) of prismatic shape magnetized in a tangential direction, inserted between ferromagnetic poles (44), according to a version known as internal magnets of radial type (“spoke-type” realization in English). The shape of the poles (44) is pseudocircular and designed to optimize the torque with and without current.

Figures 27 and 28 show two alternative embodiments of the stator (21) of the electric motor. In Figure 27, the stator has three coils (38) grouped in an angular sector close to 120 ° and the stator teeth (36a) have alternately narrow and wide angular widths as described for example in application FR2919441. In FIG. 28, the stator has three coils (38) grouped in an angular sector close to 120 ° and the stator teeth (36a) have identical angular widths as described for example in application FR2994353.

Figures 29 and 30 show an alternative embodiment of an actuator according to the invention. The actuator (1) comprises a housing (2) receiving the stator (20) of an electric motor, a cover (4) receiving a mechanical reduction gear, an intermediate plate (3) inside the actuator (1 ), as well as a printed circuit (22). The centering pins (8a, 8b) allow the positioning of the housing (2), cover (4) and intermediate plate (3) with the different centralizers: two cylindrical centralizers (not visible) made with the cover (4), a centralizer disengaged (7c) and a cylindrical centralizer (7a) present at the level of the intermediate plate (3), corresponding with -respectively- the disengaged (12c) and cylindrical (12a) centralizers present at the level of the housing (2). The fixing screws (5) are intended to fix the cover (4) on said housing (2) for closing. A connector (19) is integral with the cover (4).

Positioned axially between the intermediate plate (3) and the stator (20) is the printed circuit (22), on which are connected on the one hand - and on the housing side face (2) - the electric coils of said stator (20) and on the other hand - on the cover side face (4) - the connector tracks (19), in order to allow the power supply to the actuator (1) and the communication with it. The printed circuit is in electrical connection with the stator winding (20) by a press-fit type connector as illustrated in figure 30. On the cover side (4), the printed circuit (22) is attached to the plate intermediate (3), which promotes the evacuation of heat by conduction. The intermediate plate (3) is cut in such a way that it does not cover the printed circuit at the electrical connection level.

Claims

1. Electric actuator (1) comprising

- a housing (2),

- an electric motor comprising a wound stator (20) and a rotor (21) mounted on a rotor shaft (29),

- a printed circuit (22) used to supply said stator (20) and to control said motor,

- an intermediate plate (3),

a mechanical reduction gear (24) driven by said rotor (21) and formed by toothed wheels (45a, 45b, 45c) mounted on axes (46a, 46b, 46c),

- a cover (4),

- two centering pins (8a, 8b),

said housing (2) defining a first cavity (15) in which said stator (20) is housed, and comprising means for guiding said rotor shaft (29) on a first end,

said printed circuit (22) being located in said first cavity (15) above said stator (20),

said intermediate plate (3) being located above said printed circuit

(22),

said cover (4) defining a second cavity (25) having means for guiding the ends of said axes (46a, 46b, 46c) of said mechanical reducer (24), said cover (4) being located above said intermediate plate ( 3),

said intermediate plate (3) serving to guide the other end of said rotor shaft (29), and serving to guide the other ends of said axes (46a, 46b, 46c) of said mechanical reducer (24),

characterized in that

The first cavity (15) of said housing (2) has a first pair of centering holes receiving said two centering pins (8a, 8b),

Said intermediate plate (3) has a second pair of centering holes receiving said two centering pins (8a, 8b), Said cover (4) has a third pair of centering holes receiving said two centering pins (8a, 8b),

• said intermediate plate (3) is in contact with said housing (2) and said cover (4) on bearing surfaces (13, 14) located around the centering holes,

Two of said first, second and third pairs of holes are composed of a cylindrical centering device (7a, 9a, 12a) and a cleared centering device (7c, 9c, 12c), the cylindrical centering devices (7a, 9a, 12a) and the corresponding centralizers (7c, 9c, 12c),

• the other of said first, second and third pairs of holes is composed of two cylindrical centralizers (7a, 7b, 9a, 9b, 12a, 12b)

• said housing comprising a single seal (6) positioned at the interface between the housing (2) and the cover (4).

2. Electric actuator according to claim 1 characterized in that said housing (2) comprises a peripheral zone (16) having at least two first fixing bores (11) and in that said cover (4) comprises a peripheral zone (17 ) having at least two second fixing holes (11) so that the fixing of said cover (4) and said housing

(2) is produced by screwing using said first and second bores (11), said peripheral zones (16, 17) not being contiguous when said cover (4) and said housing (2) are supported on said intermediate plate

(3) before screwing and being in abutment and at least partially contiguous after screwing, so as to constrain and block the movement of said intermediate plate (3).

3. Electric actuator according to claim 1 characterized in that the cover (4) forms a valve body (28).

4. Electric actuator according to claim 1 characterized in that the different guide surfaces of said rotor shaft (29) and said axes (46a, 46b, 46c) of the mechanical reducer (24) are produced by the housing (2), the intermediate plate (3) and the cover (4), said guide surfaces being ball bearings (23a, 23b, 23c, 23d) or plain bearings.

5. Electric actuator according to claim 1 characterized in that said two centering pins (8a, 8b) and said intermediate plate (3) form a single piece.

6. Electric actuator according to claim 1 characterized in that the housing (2) is produced by overmolding of a plastic material and has on one of the holes of said pair of centering holes two coaxial centralizers, one cylindrical (12b), the other clear (12c).

7. Electric actuator according to claim 1 characterized in that the housing (2) is produced by overmolding of a plastic material and in that it comprises a connector (19) integrated in the overmolding.

8. Electric actuator according to claim 1 characterized in that the printed circuit (22) has a first face (33) receiving electronic components and a second (34) free face of components, said first face (33) facing the motor electric and at the bottom of the housing (2), said second face (34) facing the intermediate plate (3).

9. Electric actuator according to the preceding claim characterized in that the first (33) and second faces (34) of the printed circuit (22) are covered at least partially with a thermal paste being also in contact at least partially with, respectively, the housing and intermediate plate (3).

10. Electric actuator according to claim 1 characterized in that the wound stator (20) has stator teeth (36a, 36b) tangentially extended by magnetic field collectors (37), in that at least part of said teeth ( 36b) carry coils (38) and are attached to the stator (20) and in that said coils (38) have a frustoconical shape.

11. Electric actuator according to the preceding claim, characterized in that each stator tooth (36b) carrying a coil (38) has, with two adjacent teeth (36a), a W shape, the outer flanks of the frustoconical coil (38) being parallel to the inner flanks of said adjacent teeth (36a).

12. Electric actuator according to claim 10 characterized in that, D denotes the number of stator teeth (36a, 36b) and GAP denotes the tangential distance between the field collectors (37) between two adjacent teeth (36a), with

GAP = (360 / (8xD)) ± 5%

13. Electric actuator according to claim 10 characterized in that said rotor (21) has a magnet (35), in that E denotes the radial thickness of said magnet (35) - EP1 denotes the minimum radial thickness at the end of the field collector (37) and EP2 designates the maximum radial thickness at the birth of the field collector (37), with

EP2> 0.75xE and EP1 <EP2.

14. Electric actuator according to claim 1 characterized in that the rotor (21) comprises a permanent magnet (35) partially overmolded by an injected plastic, this overmolding partially encompassing the rotor shaft (29) and forming a plane (42 ), orthogonal to the shaft (29), on which is positioned a sensor magnet (41).

15. Electric actuator according to claim 1 characterized in that the rotor (21) comprises a permanent magnet (35) partially overmolded by an injected plastic, this overmolding partially encompassing the rotor shaft (29) and forming a sensor magnet (41).